Graphene, carbon nanotubes, and other carbonaceous materials have received increased attention for their various applications in materials chemistry, such as mechanically enforcing elements of plastics, components of light converting devices, drug delivery systems, and catalysis. It is well-known that the traditional functionalization of bulk carbon by oxidation is destructive. It has also been previously understood that the reactivity of bulk carbon is too low to be functionalized by the known non-destructive [2+3] dipolar addition of N-alkylglycine and aldehydes or Diels-Alder addition. As described herein, the inventors have unexpectedly found that the mild procedures of functionalization, previously used in fullerenes, graphene, carbon nanofibers, and carbon nanotubes, can be applied to much less reactive bulk carbon, such as carbon fibers, and enable cross-linking by introducing the furan functional group to the surface of carbonaceous materials.